For the shoulder orientation recommended in the Ellenbecker video, there is a strong case for it being a safe technique for serving - 1) Ellenbecker video recommends and Ellenbecker is a qualified researcher with a long record of publications. 2) The ATP pro servers tend to use the recommended shoulder orientation as can be seen by everyone in high speed videos. Most have a small angle, some a little more and none have the shoulders level and upper arm up. See high speed videos at impact viewed from behind. 3) The recommended shoulder orientation for the serve makes sense regarding the descriptions of what causes impingement. It does not squeeze the humerus against the acromion. I tried to work through the forces on the hanging arm and shoulder earlier. The forces are definitely very different between hanging and serving. Does the scapula turn up enough when hanging to make hanging similar to serving? Hanging from two arms, the trunk can't tilt the shoulders as in the serve. With one arm? It does not appear from the videos and descriptions on the Kirsh website that impingement is avoided in hanging. ? One hand or two? The videos talk about pressing against, bending and remodeling the Acromion. See Arm Raising Animation and Acromion Bending Animation. http://www.kirschshoulder.com/Kirsch_Shoulder/Shoulder_Imaging/Shoulder_Imaging.html Does anything on the Kirsh site talk about hanging by one arm and rotating as Posture Guy does? Why is pressing the Acromion while rotating OK? Maybe it is not pressed hanging by one arm. ? Also, some of you guys have shoulder injuries and some are undiagnosed injuries. Injuries always bring in unknowns for exercises. Hanging by a bar seems to be doing some good for some of the posters. Interesting issue.